The other day a friend of mine asked me about a way to encrypt PDF files already existent. In other words, he wanted to be able to setup a password to the files. Rapidly i tough that a fast way was to look for the tools with the keyword "linux" or "sourceforge" at the end or to search for it at Linux dedicated google search
After minor searches i found a tool that, besides other uses, did the job nicely using the command prompt.
To run it, given that the file as a ".jar" extension you need to have a Java Interpreter installed on your machine. To check wether you have Java already installed you can go to the command prompt and type "java" as a command. Bad command output means Java is not installed. Once installed the following operations will suffice to encrypt a PDF file:
Copy the file "Multivalent20060102.jar" (or a more recent version) to C:\Program Files\Java\jre6\lib\ext . This will avoid you having to set a new PATH name for the tool, as JAVA will look for it in that folder first.
Then, just use the command line "java tool.pdf.Encrypt -owner test cap.pdf" without the quotes.
This says the ownler of cap.pdf file is "owner" and has owner access to the file with the password "test"
For more usage options visit:
There may be other tools with a friendlier interface but at least this is a multi-platform solution.